Recently it is well known that, in the automobile industry, electronic control is progressing in various parts of automobiles such as throttle, brake, and intake and exhaust valves of engine. Together with this movement, rotating electric machines are being used in various parts of automobiles and the production quantity tends to increase. Therefore, reduction in cost and improvement in production efficiency are strongly required for motors and rotors.
Conventionally, fastening of a commutator and a shaft of a rotor is in many cases carried out using a method of providing a knurling on the shaft and press-fitting the commutator onto the knurling. A disadvantage in the method of press-fitting the commutator using the knurling is that contamination is likely to occur at the time of press-fitting. The commutator shaved by the knurling becomes contamination and adheres to the rotor. As a result, scratches and indentations are made on the shaft of the rotor and there is a potential to deteriorate the yield.
There is no conventional technology that has been proposed as a means for solving this disadvantage. However, as a technology for providing a motor and a commutator that can reduce an initial rupture during commutator fixing work at the time of manufacturing and a subsequent creep rupture over time, has excellent molding workability for the commutator, can improve the coaxial accuracy between the commutator and the shaft, and can improve the productivity, a commutator has a structure in which a plurality of conductors integrally molded with resin are arranged in a cylindrical shape on an outer circumference, an inner circumferential surface of the resin of the commutator has a tapered shape, a diameter φ is minimum at an intermediate portion, the diameter becomes larger as it goes closer to an end portion. A motor characterized in that a commutator is made of resin and its inner circumferential surface has a tapered shape whose inner diameter is minimum at an intermediate portion and becomes larger toward both ends, and a shaft is press-fitted and fixed to the inner circumferential surface of the commutator has been proposed.